1. Field of the Invention
The present invention relates to orthopedic instruments and more particularly, to an interlocking bone plate system for rigidly affixing bone segments.
2. Description of the Related Art
Conventionally, a bone plate and screws are used in surgery for fixation of a comminuted or osteoporotic fracture. By means of the engagement force between the screws and the bone and the friction force between the bone plate and the bone, the bone plate is affixed to the surface of the bone at one side. This fixation method is not stable due to the fact that when the load from the patient during a movement of the patient is greater than the friction force between the bone plate and the surface of the bone, the bone plate may be forced to display, biasing the screws. Further, if the bone plate is not closely matched in configuration with the bone, or if the screws are fastened excessively tight or the bone bears an excessive load, bone repositioning after surgery may be destructed.
Due to the aforesaid drawbacks of conventional surgery, a new locking plate is created for healing a broken bone. A locking plate of this design has an inner thread in each screw hole thereof for engagement with an outer thread around the periphery of the head of each screw. Thus, when a locking plate is locked to a broken bone by screws, the locking plate is not kept in direct contact with the surface of the broken bone, minimizing bone contact surface area, avoiding periosteal compression, facilitating quick bone healing and enhancing structural stability.
However, the biodynamic effect of the fixation of the aforesaid new locking plate is still obscure. Further, a locking plate system of this design is quite expensive and requires a specifically designed surgical implement during surgery. Further, if the bone receives an excessive muscle tension or load after surgery, the fixation cannot sustain inverse deformation of the bone, leading to surgical failure.